Why do police composite sketches never look even vaguely human?

Apparently in St. Louis, some sort of human-turtle hybrid is molesting girls.
http://www.stltoday.com/news/local/crime-and-courts/st-louis-police-release-sketch-of-man-who-fondled-girls/article_e46d07a2-db2c-11e1-a9df-001a4bcf6878.html

I've always thought of that job as being really difficult. You're asking people to tell you everything about a person that just did something horrible to them. Then you're attempting to accurately draw a person you've never seen. Then you're forced to show these people a drawing of a face you hope resembles the person who just did something horrible to them. Then you ask for constructive criticism.